A water-soluble mold release agent is easy to treat and is widely adopted as a mold release agent for a die casting metal mold. Commonly, mineral oil, animal oil, vegetable oil, silicon oil, wax, fatty acid or the like is emulsified by a surface active agent and is distributed as the water-soluble mold release agent. The water-soluble mold release agent is used in the state of emulsion diluted with water of suitable amount.
The water-soluble mold release agent is applied on the mold surface of the hot die casting metal mold by spraying. In this case, most water included in the water-soluble mold release agent is vaporized, whereby the water-soluble mold release agent is promoted to adhere to the mold surface, and the metal mold is cooled.
When the water-soluble mold release agent is applied on the mold surface, a reactant, whose main component is iron oxyhydroxide FeOOH, and is oxidized by drying so as to become ferric oxide Fe2O3. Accordingly, the reaction product of Fe2O3 is formed on the mold surface after applying the mold release agent thereon.
Well, at the time of casting, oxide film may be generated on a surface of molten metal injected into the metal mold so as to spoil fluidity of molten metal, thereby causing casting defect such as misrun. For solving this problem, an art is proposed so that a mold release agent, which contains a metal hydride, such as calcium hydroxide, sodium hydroxide or lithium hydroxide, as a deoxidizing agent, is applied on the inside of the metal mold, and the casting is performed while the oxide film of the molten metal is deoxidized by the deoxidizing agent resolved by the heat of the molten metal (the Japanese Patent Laid Open Gazette 2004-154833).
At the time of spraying the water-soluble mold release agent to the metal mold, water is vaporized suddenly and dryness occurs. Accordingly, impurities and deteriorated materials adhere to the mold surface, thereby causing the filth of the metal mold. For solving this problem, an art is proposed so that a specific metal chelating agent is mixed with the mold release agent, whereby the filth of the metal mold is prevented while maintaining the function as a mold release agent (the Japanese Patent Laid Open Gazette 2003-275845).